Steve Mirsky: Welcome to the Scientific American podcast Science Talk, posted on February 26, 2014. I am Steve Mirsky. Earlier today NASA announced that its Kepler mission had discovered 715 new exoplanets orbiting 305 different stars, which immediately made obsolete some of the details of the discussion you’re about to hear with journalist Lee Billings. Lee is the author of Five Billion Years of Solitude: The Search for Life Among the Stars. And even though the specific numbers of exoplanets we now know about is different from when we recently talked, the larger points remain, well, larger and on point. We spoke at Scientific American.

Lee, I think a lot of people have heard of the Drake Equation, but what was new to me in reading the book was the story behind the Drake Equation, basically he comes up with it a couple of days before this big conference he had organized. Tell the story; it’s really interesting.

Lee Billings: So that’s the story that he’s told, and-

Steve Mirsky: Well, first tell what the Drake Equation is for anybody who doesn’t know.

Lee Billings: Yes. Yeah, so the Drake Equation is something that the radio astronomer Frank Drake came up with really right after his first search for extraterrestrial intelligence. He was the first guy to really get the notion of pointing a big radio telescope at nearby stars to look for radio transmissions from other cosmic civilizations that might be out there. And shortly after he did that, that was called Project Ozma back in the early 1960s, he had a – he organized a meeting that was taking place at the Green Bank Observatory, where he worked, and invited all these luminaries to come and help him figure out what the chances were for SETI to be successful. So some of the people who came-

Steve Mirsky:SETI, search for extraterrestrial intelligence?

Lee Billings: Yes. Yes. Yes. If I – yes, search for extraterrestrial intelligence. And he invited people like Carl Sagan, who at the time was probably the least-famous, least-renowned person who showed up.

Steve Mirsky: He was 27.

Lee Billings: He was, yeah, very young, 27 at the time, but he was already making his mark. He invited three Nobel Prize winners – well, actually two Nobel Prize winners, Harold Urey and – oh gosh-

Steve Mirsky: Josh Lederberg.

Lee Billings: That’s right. So you know my book better than I do. Josh Lederberg. And then actually a third person got the Noble Prize as they were meeting, and that was I believe Melvin Calvin. So there were three Nobelates there, there were a handful of other people there, and they all came together to try to just hammer out what the chances were that SETI could be successful.

So before the meeting Drake secluded himself in his office and was scribbling with some paper and started to put down the different variables, the different things that could influence whether or not SETI could be successful. So those are things like the rate of star formation in the universe, how often abodes of life form, the number of stars that bear planets, the number of planetary systems that have habitable planets, the number of habitable planets where life actually arises. And it’s a series of little variables like that, and you kind of string them all together and it will give you some estimate at the end when you multiply them all together that will maybe not tell us how many alien civilizations are in our galaxy, but it will certainly quantify our ignorance, so to speak; it will tell us what we know and what we don’t know.

Steve Mirsky: Now these variables, back when he did it, what year is it approximately?

Lee Billings:I think it was 1961.

Steve Mirsky: Okay, so, you know, you’re spit-balling a lot of the variables compared to the kind of information that we have today, which is still pretty dicey.

Lee Billings: That’s right. That’s right. And if you look at the equation kind of left to right, you know, it does start with things like star formation, planetary system formation, habitability on a planet, the rise of life. These are things that as we progressively sweep kind of through the equation it starts with things we know very well. We know pretty well the rate of star formation in the Milky Way. We even knew back then that – we suspected that planets were common around stars. We didn’t really know, we suspected. And now we kind of do know that. And you move further down the equation, you get things that are really just in the realm of the social sciences, that don’t have anything to do with astronomy. So you get things like how long a civilization lasts, whether or not a civilization develops some kind of technology that we can detect, how often intelligence arises out of life, simple life arising.

So we still don’t know a lot of kind of the latter aspects of the equation, but, you know, maybe we could close in on those relatively soon. That’s really what the book’s about, about this quest to try to find our place in the greater outward universe.

Steve Mirsky: So the equation, even at the time, though, yielded some interesting estimates.

Lee Billings: Yeah. Yeah. Well, it’s funny, because it all ended up coming down to l. So each one of these little variables in the equation has a little number or rather associated with it. So something like the number of habitable planets, I believe is called ne, and, you know, so there’s all these different little variables and they all have these little names, and the thing is is that they all seem to cancel each other out when they were considering the possible values that were within the realm of reason. And what ended up coming to – they ended up coming to a conclusion essentially that what really seemed to dictate the number of I guess other civilizations that we share the Milky Way with was how long a civilization, a technological civilization like ours typically endures and survives on its planet. And the reason behind that is a little complicated, but essentially if you think about it, the Milky Way galaxy is, you know, about 100,000 light years wide, I think; it’s got hundreds of billions of stars. Well, let’s say that the nearest civilization to us is 50,000 light years away, halfway across the galaxy. Well, if a civilization only lasts let’s say 25,000 years; that’s quite a long time, but let’s say, you know, technological civilization lasts 25,000 years, that means that we could see them out there maybe. Their signals would get to us if they were broadcasting at us, but by the time they got to us they would already be gone.

Steve Mirsky: Right. By the time it got here or by the time we sent something back-

Lee Billings: That’s right.

Steve Mirsky: There’s a certitude that no one would be there to hear it.

Lee Billings: So yeah, it just all seemed to come down to the question of how long civilizations can last on planets. And that was kind of the conclusion of the conference. And, you know, of course, in terms of the actual values that were bandied about, I think Drake kind of had a moment where he stood up and basically said, “Okay, well, it could either be, you know, a few tens of thousands of years on the outside, or maybe it could be geologic time scales that civilizations can last. Maybe if they manage somehow to get through their technological adolescence, that notion of, you know, kind of little kids with nuclear bombs and things like that, really dangerous time, maybe then they can actually endure and last for, you know, you have these geological time scales of billions of years; maybe they can last until their sun burns out. Obviously depending on what you think the value of l is, depending on what you think the average lifetime of a civilization is, that greatly influences and affects what you expect to see out there.

Steve Mirsky: I forget if the quote is in the book, and I think it’s from Buckminster Fuller, it says, “Either there is, you know, millions of other civilizations or we’re the only civilization, and either way it’s pretty mind-boggling.”

Lee Billings: Yeah, Bucky Fuller said that, and then Arthur C. Clarke had his own version, you know, “either prospect is terrifying.”

Steve Mirsky:Right.

Lee Billings:So, yeah, you know, it’s something that’s a pretty common thing I think to think about in science fiction and in science. You know, we don’t really know obviously the answer yet. We only have a sample size of one. We can only look at ourselves and the trends in our own societies right now and look at what we’re doing to the planet and try to extrapolate from that. And is that scientific? Uh, you know, it’s pretty dicey.

Steve Mirsky:So the book basically is in two large parts. There’s the search for exoplanets and then there’s the idea of trying to figure out whether any of those exoplanets might harbor life. But you tell the story in many ways through these individuals who you spoke to. So why don’t we just talk about some of them.

Lee Billings: Sure.

Steve Mirsky: Geoff Marcy or Greg Laughlin.

Lee Billings:Yeah. Yeah. Well, you know, Geoff Marcy is – we come to him relatively early in the story, and that’s because he is one of these founding figures of what I like to call the exoplanet boom, this kind of miraculous era we’re living in right now, where, you know, thousands of planets are literally pouring out of the – well, not literally, but they’re pouring out of the sky and we’re just finding them everywhere we look.

Steve Mirsky: Fortunately figuratively.

Lee Billings: Yes. Yes, fortunately figuratively. Worlds colliding is not good. But Geoff Marcy back in the – his program I believe started in the late ‘80s actually, and he was looking for planets, things like Jupiter around nearby stars. Couldn’t find any.

Steve Mirsky: Jupiter because it would be the easiest thing to find-

Lee Billings: That’s right.

Steve Mirsky: -‘cause it’s freaking big.

Lee Billings: Yeah. Exactly. Exactly. So they’re looking for kind of this thing called – well, I like to call it a wobble, where they’re looking for actually the motion that the planet induces upon its star as it whirls around the star. So just in the same way the star kind of tugs on a planet, a planet actually tugs on a star too. And that wobble back and forth isn’t really great, but for Jupiter that’s kind of the best you’re going to get for our solar system.

But so he and a partner-

Steve Mirsky: Like the moon pulls on the Earth’s oceans.

Lee Billings: Exactly. Exactly. Same kind of thing. And he and a partner, Paul Butler, started looking, you know, really ramping up in the early ‘90s, looking for these things, for Jupiters around nearby stars, and they just couldn’t find anything. And they were just thinking, “Gosh, this is so hard. We’re never going to succeed. We’re never going to succeed.” And then what happened is actually a competing team led by – well, those two guys, two Europeans, Michel Mayor and Didier Queloz in 1995 actually found the first hot Jupiter, the first exoplanet found around a sun-like star. And that’s something that, you know, is about the size of Jupiter but it orbits kind of hellishly close, way within the orbit of Mercury around a star, something that no one really thought could exist through all the theories of planet information and disarray. And Geoff Marcy and his partner Paul Butler went back through all their data, they had accumulated a lot of data by then and they found and confirmed the planet that Mayor and Queloz had found, and then they started finding more and more and more. And the pace of discovery just accelerated from there and it’s still accelerating today, and there’s no real sign that it’s going to slow down.

Steve Mirsky: And we’re finding new exoplanets now every week, or their publication announcing the discovery of them is weekly.

Lee Billings:Yeah. I mean I would say it’s almost every day now, not necessarily publication, but finding them. I mean you look at the numbers. A friend of mine showed me a slide; he thought it was an up-to-date slide last week. He tweeted something at me and he was like, “Look at all the planets we’ve found.” It was from Kepler and it was, you know, something on the order I think of 2,500 candidate planets. That was from January. Well, last week they released new data, now it’s 3,500 planets. So in that time there’s been 1,000 planets added. You know, you can do it up day by day and we’re finding things every day. We found more than 1,000 that are confirmed, so yeah, they’re everywhere. And Geoff Marcy kind of helped kick that off.

And his story is really interesting because it kind of gets at this really tricky notion of how we’re kind of forced to find most planets right now, which is that we’re finding them indirectly; we’re not finding them by actually imaging the planet itself, taking a picture of it, which is what a lot of people think astronomy is about. Instead we’re finding them through these very indirect measurements, these wobbles and little diminutions of starlight and things like that, that we see.

Steve Mirsky: Right, when the planet goes in front of the star, if we’re at the correct orientation you get this tiny little drop in the sunlight or starlight that we’re able to measure. And if that’s a regular pattern it’s pretty clear that something is orbiting that star.

Lee Billings:Yes. Yes. And so that’s called a transit. So we have the wobbles and the transits and they’re both relatively indirect. And there’s a statistical nature to this, where, you know, you’re taking measurements; you have to accumulate a lot of measurements, very fine measurements over time, and gradually a signal will emerge, in particularly for these small, potentially Earth-like planets. So, you know, if it’s a big hunk of gas that’s orbiting hellishly close to its star that’s pretty easy to see and that pops out really quickly, but if it’s something small it can take years and hundreds or thousands of measurements. And it will just barely be on the cusp of statistical significance. So there are lots of false starts and false positive and stories of people being fooled by planets that weren’t actually there. And there are some that are in our kind of bestiary right now of potentially habitable planets that are out there that some people question, and Geoff Marcy has kind of been at the forefront of all of that. So that’s kind of what I tell the story in the book. And it goes on from there, so.

Steve Mirsky:And Guy Laughlin is this theoretical astrophysicist?

Lee Billings: Oh yeah, yeah, yeah. Greg Laughlin actually is-

Steve Mirsky: I’m sorry, Greg Laughlin.

Lee Billings: He’s a guy, Greg Laughlin.

Steve Mirsky: He’s a guy.

Lee Billings: He’s a great guy, actually. He is an astrophysicist at the University of California, Santa Cruz. And one thing that’s special about Greg is he is one of the deepest thinkers about this that I’ve ever encountered, and he has a lot of unconventional ideas about the search for exoplanets, how we can find them, where it’s going to go in the future. And most importantly for me, one thing that makes him very distinctive is he – I guess he suffers fools gladly, because I approached him very early on and he kind of was one of the first people to introduce me to the subject and kind of show me the potential and show me this kind of coming revolution and forecast what was going to happen.

So the story, really quickly, is that in 2007 I was talking to him kind of randomly for a story very slightly about exoplanets, just about how we detect them, which we’ve just gone through here in this podcast. And he had me do a little exercise where he basically said, “Okay, you know, take all the planets we know, take the record-holding planet each year, the lowest mass exoplanet we know year by year and track that on the y axis, graph that on the y axis, the lowest mass one. On the x axis you just go year-by-year. So what’s the lowest mass one in 2007 or 2008 or 2009?” And then you draw a trend line through the data and what you get is just this gorgeous straight line that just leads straight down to an Earth mass planet in 2011. So he told me this in 2007 and I was just like, you know, “Oh my gosh” – really a lot of expletives came out of my mouth when he told me that, ‘cause I was just kind of flabbergasted, because here is this situation where we’re about to find other, you know, Earth signs, Earth mass, potentially Earth-like planets in just a few years. And no one was really talking about it. I mean some people in the science media were talking about it, but, you know, you talk to the average person on the street and they didn’t even know about exoplanets; they didn’t even know that we were potentially so close to finding, you know, Earth 2.0, a mirror Earth. And that just really excited me and it kind of made me feel a little strange. You know, why was it that we were on the cusp of this potentially revolutionary discovery and yet most people didn’t know about it.

So he was my entrée into the whole field and he was the one who really introduced me to it and yeah, it kind of went from there.

Steve Mirsky: Now this whole realm is not just limited to astronomers/astrophysicists; you talk about Mike Arthur, who is a geologist.

Lee Billings: Yeah. Yeah. Well that’s kind of a funny story, because the reason why it’s not limited to astronomy and astrophysics is because obviously we have to start from what we know. When we’re looking for other Earths that obviously implies we’re looking for things like us. If you want to become an expert, if you want to know and pontificate about Earth-like planets, you have to become an expert on the Earth. You have to really know what the Earth, how it formed, what it’s like, what it used to be like 3 billion years ago, what it’s going to be like 3 billion years from now. And that takes us into this totally different realm. We are not talking about, you know, stars and galaxies and things like that so much as you’re talking about, you know-

Steve Mirsky: Dirt.

Lee Billings: Dirt, that’s right. Earth. And Mike Arthur is a sedimentary geologist at Penn State and it was really fortuitous, kind of totally random fluke that we even met. He’s very involved in the Marcellus shale and questions about whether or not the Marcellus shale should be totally exploited via fracking, hydrofracking to release all its deposits of natural gas. Some estimates suggest that the Marcellus shale contains enough natural gas – enough recoverable natural gas to supply the U.S.’s energy needs for 30 years, 20 years, maybe even 100 years, depending on how much we use and whether we sell it or not.

Steve Mirsky: And whether we care about the effects of global warming.

Lee Billings: Yeah. Exactly. So I ended up kind of talking to him in a very roundabout fashion, where I was talking to another researcher at Penn State, Jim Kasting, who is kind of an expert in planetary habitability and how planets maintain habitable climates over very, very long periods of time, over billions of years of time. And Jim had to go basically teach a class at one point, and he just dumped me in Mike Arthur’s office and we started talking about the Marcellus shale and, you know, heck, how did all that carbon, how did all that energy, how did all that natural gas get locked in those rocks? What does that mean? And we just started talking about it, and I realized as we were talking that there’s a big connection between that one event and this one place on the planet, and kind of the bigger picture that we’re seeing unfold around us in terms of climate change right now, climate change in the past, how life at times in the Earth’s history has essentially reached out and gained a planetary influence, a global influence, and it’s able to kind of wrench the machinery of the planet, the geochemical systems of the planet into very different configurations. We’re doing that right now.

Other organisms in the past have done that. So, you know, the colonization of land by plants and eventually by animals kind of threw the climate out of whack and caused some glaciations and mass extinctions. Way, way, way before that, about 2.5 billion years ago there were these little single-celled organisms called cyanobacteria, a whole class of them, that figured out how to split water using sunlight and harvest the hydrogen from the water to drive their metabolisms and power their bodies basically. And what they did is they vented out all the oxygen from that. You know, water is H2O, so they took the hydrogen, they vented all the oxygen out, and that caused a huge mass extinction, probably one of the greatest ones in our planet’s history. It totally changed the way the planet, you know, was. We go from this anoxic oxygen-free world to what we have now, where the atmosphere is 21-percent oxygen and we have not just single-celled life, but, you know, big hunks of meat that can talk to each other, like you and me.

So, you know, the story that Mike Arthur told me showed me that, you know, this is all kind of one spectrum of the planet’s past. And I guess one thing that’s kind of interesting – this is a little bit rambly, I know – but what’s interesting is that this ties into what we’re looking for out there. When we look for other Earth-like planets we’re looking for these same signs of life, whether it’s people, you know, whether something intelligent like us, and having high technology changing the planet, or whether it’s something like cyanobacteria or some kind of primitive life that’s changing the planet. The point is that these sorts of changes that we’ve been discussing, the oxygenation of the Earth’s atmosphere, the total transformation of the Earth’s cycles and parts of its surface by us, these are things that in theory you could detect across interstellar distances using big space telescopes. And I just kind of wanted to underpin that for the reader and try to explain how they’re all connected.

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